As mobile devices have been increasingly developed, and the demand for such mobile devices has increased, the demand for secondary batteries has also sharply increased. Among such secondary batteries is a lithium secondary battery exhibiting high energy density and operating voltage and excellent preservation and service-life characteristics, which has been widely used as an energy source for various electronic products as well as for the mobile devices.
However, various combustible materials are contained in the lithium secondary battery. As a result, there is a possibility of danger in that the lithium secondary battery may overheat or explode due to overcharge, overcurrent or other external physical impact. In other words, the lithium secondary battery has low safety. Consequently, safety elements, such as a positive temperature coefficient (PTC) element and a protection circuit module (PCM), to effectively control an abnormal state of the lithium secondary battery, such as overcharge or overcurrent, are mounted in the lithium secondary battery in a state in which the safety elements are connected to a battery cell of the lithium secondary battery.
Generally, the PCM is connected to the battery cell via conductive nickel plates by welding or soldering. That is, nickel plates are connected to electrode tabs of the PCM by welding or soldering, the nickel plates are connected to electrode terminals of the battery cell by welding or soldering so that the PCM is connected to the battery cell, and an insulative top cap is fitted onto the top of the battery cell, thereby manufacturing a battery pack.
It is necessary for safety elements, including such a PCM, to be maintained in electrical connection with electrode terminals of a battery cell and, at the same time, to be electrically isolated from other parts of the battery cell. A plurality of insulative mounting members is necessary to achieve such connection with the result that a process of assembling a battery pack is complicated, and the size of a space to receive the battery cell is reduced.
Also, the aforementioned method of connecting the PCM to the battery cells via the nickel plates and coupling the insulative top cap to the top of the battery cell to manufacture the battery pack is constituted by successive processes. For this reason, defects at one process are connected to defects at another process with the result that it is difficult to reduce a defect ratio and to manufacture a battery pack through outsourcing.
Consequently, there is a high necessity for technology to integrate components, such as a PCM, a top cap and insulative mounting members while maximally utilizing a conventional battery cell and a conventional assembly method, thereby improving quality of a battery pack, to achieve stable coupling between members disposed at the top of the battery cell, and to increase the capacity of the battery cell.